This invention relates in general to raise boring or box hole drilling bits and in particular to improvements to enhance cuttings removal. 2. Background Information
In the raise boring method or process a large diameter bit body, upon which rotatable cutters are dispersed, is pulled upwardly and rotated by a drill string attached to a stem that protrudes upwardly from the bit body.
Cuttings formed while raise boring fall downwardly against the bit body and, in the past, accumulated to the extent to sometimes impede progress. The same problem can exist in box hole drilling.
Various attempts have been made to prevent the accumulation of cuttings on the bit body and around the rotatable cutters. Some of the solutions of the past involve the formation of openings in the bit body to permit the flow of cuttings through the bit body and prevent accumulation. Even though progress has been made toward solving this problem, there still exist a cuttings accumulation problem in the immediate vicinity of the cutters. This can lead to a variety of problems, including damage to the seals used to contain lubricant in the bearings that supports the cutters.
There is, as a consequence, need for additional improvement in raise boring or box drilling bits to prevent the accumulation of cuttings around the rotatable cutters supported on the bit body.